LA55-P
LEM LA55-P closed-loop Hall current transducer, 50 A nominal with ±70 A range, ±12 to ±15 V supply and PCB mounting.
The LA55-P is a LEM closed-loop Hall current transducer with a 50 A nominal primary current and a measuring range of about ±70 A, mounted directly on a printed circuit board. A closed-loop (compensated) design drives a secondary current that exactly balances the primary ampere-turns, so the output tracks the primary with high accuracy and very low offset drift over temperature. The transducer provides galvanic isolation between the primary conductor and the secondary circuit, protecting the control electronics from high common-mode voltages in motor drives, inverters and power-conversion equipment. Its fast response and wide bandwidth make it a frequent choice for field-oriented motor control, where an accurate, low-noise phase-current signal is essential for correct torque and speed regulation. The ±12 to ±15 V bipolar supply suits conventional analog control boards, and the compact PCB module simplifies assembly in three-phase drives, servo amplifiers and welding supplies. Because the same transducer covers 0 to ±70 A, a single part can serve several power levels, which simplifies inventory across a product family. Every LA55-P BeiLuo ships is a genuine LEM part, factory-traceable and supplied with an import declaration, a certificate of origin and a RoHS compliance file. For new designs, consider the LTS25-NP when a single +5 V supply is preferred, or the open-loop HLSR range when cost and size matter more than accuracy.
FAE Professional Review
The LA55-P is the workhorse of our closed-loop current-sensor lineup. Engineers choose it when a motor drive needs an accurate, low-drift phase-current signal and the control board already has a bipolar analog supply. It is forgiving to use, but keep the primary conductor centered in the aperture and size the measuring resistance for the ADC input range.
| Parameter | Value |
|---|---|
| Technology | Closed-loop Hall |
| Nominal Current | 50 A |
| Measuring Range | 0 to ±70 A |
| Supply | ±12 to ±15 V |
| Mounting | PCB |
| Temperature | 0 °C to +70 °C |
Application Circuits
Motor drive phase-current feedback
Reference circuits and application schematics for Motor drive phase-current feedback are available from our FAE team.
Servo inverter current loops
Reference circuits and application schematics for Servo inverter current loops are available from our FAE team.
Welding and induction power stages
Reference circuits and application schematics for Welding and induction power stages are available from our FAE team.
Need a reference schematic or design review? Our FAE engineers can share verified circuits and layout guidance for this part.
Related Documents
Alternative Part Numbers
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Frequently Asked Questions
What projects suit the LA55-P?
It suits motor drives, servo inverters and welding power stages that need an accurate, low-drift phase-current signal and have a bipolar analog supply. The 50 A nominal and ±70 A range cover a broad band of medium-power designs.
For a single +5 V control board, consider the LTS25-NP instead.
How do I set the measuring resistor?
The output is a current, so a measuring resistor converts it to a voltage for your ADC. Choose the resistor so the maximum expected current produces a voltage within the ADC range, and respect the maximum measuring resistance in the datasheet at your supply.
Our FAE team can confirm the resistor for your supply and ADC.
Is the part genuine and what documents ship with it?
BeiLuo supplies factory-traceable LA55-P parts with an import declaration, certificate of origin and RoHS file on every order. Stock is normally available and the datasheet downloads from this page.
Order a sample to validate the sensor before volume production.